جستجوی مقالات مرتبط با کلیدواژه « اثر غالبیت » در نشریات گروه « زراعت »

Increasing rice production is one of the demands of the world market and one of the goals of many countries that produce this staple crop. Development of high yielding cultivars is one approach and perhaps the only one to supply the country's rice demand. Knowledge of the genetic parameters that control different traits, including heritability, the average degree of dominance, and gene action is very important in choosing a breeding scheme that lwads to development of improved high yielding cultivars. The diallel designs proposed by Griffing, Jinks, and Hayman provide information about the genetic suitability of parents to be used in breeding programs. This experiment was carried out to estimate the combining ability and the type of gene action of eight Central and Western Asian rice varieties using diallel crossing design.

In this experiment, eight rice varieties from Central and West Asia were used as the parents of the crosses. The progenies obtained from the diallel crossing design along with their parents were grown using randomized complete block design with three replications in the experimental field of Rice Research Institute of Iran, Rasht, Iran. During the growth duration, according to the standard evaluation method of the International Rice Research Institute (IRRI), the necessary evaluations for agro-morphological characteristics were carried out. Diallele analysis was performed using the second Griffing method under the first model (with fixed effect). Baker's ratio was used to determine the contribution of additive variance in the genetic control of studied traits. Also, diallel analysis proposed by Morley Jones method done to estimate gene actions and genetic variance components (additive and dominant). SAS 9.4 and DIAL98 softwares were used to perform preliminary variance and diallel analysis.

The results of diallel analysis by Griffing method to estimate combining ability showed that general and specific combining ability were significant for all studied traits which indicated the importance of additive and non-additive effects in the genetic control of these traits. Baker's ratio for grain yield, number of fertile tiller number per plant and number of filled grains per panicle showed that non-additive gene effects had a significant contribution in the genetic control of these traits. The value of Baker's ratio in plant height, panicle length and number of days to 50% of flowering indicated the presence of additive and non-additive gene effects in the genetic control of the aforementioned traits. Evaluation of general combining ability showed that the highest combining ability was observed in D3, Ghadeer, Atai-1 and Hashemi cultivars for grain yield, fertile tiller number per plant, filled grains per panicle and panicle length, respectively. Also, D3 and Marjan cultivars had the lowest general combining ability for plant height and days to 50% of flowering. The estimation of specific combining ability showed that for grain yield, Atai-1×Marjan cross, for fertile tiller number per plant, Ghadeer×Atai-1 cross, for filled grains per panicle, Marjan×Atai-1 cross and for panicle length, Ghadeer×Marjan cross had the highest specific combining ability. The estimation of genetic parameters of diallel genetic analysis showed that the contribution of non-additive gene effect in the genetic control of grain yield, fertile tillers per plant, plant height, filled gains pe panicle and panicle length was higher than additive gene effect.

considering the resuts of this experiment, it can besuggested that D3 cultivar is suitable parent for increasing grain yield as well as reducing plant height, and Marjan cultivar is suitable parent for shortening growth duration, in targeted crosses. The results also showed that Atai-1×Marjan cross had the highest specific combining ability for grain yield. Therefore, this combination is suggested for the development of high yield potential hybrid rice cultivars. The best combination for shorter plant height was Jalal×Atai-1 cross. The estimation of genetic parameters of diallel analysis showed that designing breeding schemesfor development of hybrid rice cultivars to improve grain yield and reduce plant height will be promising. The results also indicated that the use of selection method to reduce the length of growth duration will be possible.

Drought is the main abiotic stress seriously influencing wheat production and quality in Iran. Information about genetic controlling drought tolerance inheritance is necessary to determine the type of breeding program as well as develop tolerant cultivars. In this study, Bayesian inference using LASSO method used to identify the most important gene effects related to drought tolerance in context generation mean analysis. For this purpose, field experiments consist of two pairs of crosses with non-tolerant and tolerant cultivars and generations derived from them were carried out across two years as split plot designs based on RCBD with three replications in which main plots assigned to irrigation treatment consist of two levels (well watered and cessation of irrigation at pollination stage) and sub-plots given to the generations. Bayesian inference is an alternative approach which combines available prior knowledge (prior distribution) with the information contained in the data. The result is the posterior distribution containing all information to interpret genetic structure. LASSO is an effective method to apply shrinkage and selection on model variables. Non-important effects in the model shrunk toward zero and excluded from the model. While for important effects, less shrinkage will be achieved. Since the additive, dominance and epistatic gene actions involved in drought tolerance inheritance, methods which utilize all type of gene effects, like recurrent selection followed by pedigree method may be useful for drought tolerance stress improvement.

To determine the type of genes action and estimate genetic parameters under moisture stress condition, two inbred lines of S0200237 (P1) and ILYH0231 (P2), sensitive and resistant to moisture stress, respectively, were crossed in 2013. Six generations P1, P2, F1, F2, BC1 and BC2 were planted in a randomized complete block design in 2015 and generation mean analysis was performed. Significant and positive heterosis was observed for ear biomass/ plant and ear-grain yield/plant. The joint scale test and the average of gene dominance confirmed the inadequacy of the additive-dominance model for most traits, indicating the importance of epistatic and over-dominant effect in genetic control of the traits. The results showed that row number/ear, ear diameter, cob diameter and grain depth were controlled by additive effect. The broad and narrow sense heritability of the ranged varied from 68.9 to 88.6 and 13 to 50.40, respectively. The average of genes number controlling the traits varied from 1-7 genes for grain yield. The maximum positive heterosis was observed for ear biomass and grain yield per plant. Generally, selection in early generations for grain yield-related traits with high narrow sense heritability, including the number of rows per ear, will improve grain yield in advanced generations. In addition, selection in early generations to reduce cob percent, to some extent, does not result in a significant reduction in total ear weight, and will result in an increase in harvest index, thus improves grain yield under moisture stress conditions.

This study was carried out to investigate the genetic structure of the 36 maize hybrids established from eighteen female lines and two male testers according to line × tester method under normal irrigation and drought stress conditions. Two separate experiments، normal irrigation and drought stress at grain filling stage were performed in Moghan for two years، using a RBCD with three replications. The results showed that the effect of gene action could be both non-additive and additive in the expression of grain yield under both conditions. However، GCA/SCA variance ratio revealed that non-additive genetic variance was more important for grain yield than additive variance. Analysis of general combining ability indicated that the variation of combining ability of lines in non-water stress condition was higher than that in water stress condition. The reactions of general combining ability of lines in both conditions were not similar. Lines L8، L11 and L17 in normal irrigation and lines L15، L16 and L17 in stress condition showed better general combining abilities for grain yield. The K3653/2 tester showed better general combining abilities for grain yield in both conditions. The crosses such as L1×T1، L4×T1 and L8×T1 in normal irrigation condition and L9×T2 in drought stress condition showed better specific combining abilities for grain yield.

To determine mode of action of the genes affecting important agronomic traits and seed shattering resistance in soybean، progenies derived from crosses between Telar and T215، including F1، F3، BC1، and BC2 together with P1 and P2 were evaluated in Karaj. The results indicated that for all the traits، genes action with dominance effects، followed by additive effects had the most impact on the genetic performance. There was a high similarity in inheritance of the reproductive-related characters such as flowering initiation with starting stage of seed filling، completion of seed filling with seed maturity، seed yield with yield components especially with pod number per plant and plant height with number of node per stem. Dominance effects in seed shattering were more important than the additive effects. However، epistatic effects could not be ruled out. [d]، [h] and [i] effects were significant for majority of agronomic traits and [j]، [l] interaction effects were significant for a few traits. Inheritance mode of flowering initiation (R1) was similar to initiation of seed filling (R5)، compelet seed filling (R6) was similar to compelet maturity (R8)، seed yield was similar to its components and plant height was similar to number of nods. Seed shattering had single gene inheritance but different epistatic effects inpressed expersion of the character.

The genetic structure of agronomic traits has the most important role in determination of breeding methodology. Generation means analysis and QTL mapping refers to effective methods for determination of gene type and action. In order to investigate the genetic structure of agronomic traits of Gharib × Khazar via means analysis, six basic generations in three replications as randomized complete block design were cultivated at Gonbad Higher Education Center in 2008. At the same time, in order to map agronomic traits, 20 plants of 192 F3 families and parents were planted. The results showed gene controlling of plant height, panicle length and biomass indicated over dominance, grain number, branches number, days to flowering, panicle extraction and flag leaf length showed partial dominance. Significant additive effects were detected for grain number, branches number, days to heading, plant height and panicle extraction. Therefore, the selection method is useful for improving these traits. The three paramedic models were detected for branches number, plant height, panicle length, panicle extraction, days to heading, panicle extraction and flag leaf length and width. Mapping of agronomic traits showed that qHD-1b, qPL-12, qNP-2, qDWS-8, qWFL7, qWP1, qWP-11a and qWP11b explained more then 20 percent of total phenotypic variation. The comparison of the two methods showed that, with the aid of selection for some QTLs such as qHD1b, can be used for decreasing days.